In a typical radio communications network, wireless terminals, also known as mobile stations and/or user equipments (UEs), communicate via a Radio Access Network (RAN) to one or more core networks. The RAN covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a radio base station (RBS), which in some networks may also be called, for example, a “NodeB” in Universal Mobile Telecommunications System (UMTS) or “eNodeB” in Long Term Evolution (LTE). A cell is a geographical area where radio coverage is provided by the radio base station at a base station site or an antenna site in case the antenna and the radio base station are not collocated. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. Another identity identifying the cell uniquely in the whole mobile network is also broadcasted in the cell. One base station may have one or more cells. A cell may be downlink and/or uplink cell. The base stations communicate over the air interface operating on radio frequencies with the user equipments within range of the base stations.
In some versions of the RAN, several base stations may be connected, e.g., by landlines or microwave, to a controller node, such as a radio network controller (RNC) or a base station controller (BSC), which supervises and coordinates various activities of the plural base stations connected thereto. The RNCs are typically connected to one or more core networks.
A UMTS is a third generation mobile communication system, which evolved from the second generation (2G) Global System for Mobile Communications (GSM). The UMTS Terrestrial Radio Access Network (UTRAN) is essentially a RAN using Wideband Code Division Multiple Access (WCDMA) and/or High Speed Packet Access (HSPA) for user equipments. In a forum known as the Third Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for e.g. third generation networks and further generations, and investigate enhanced data rate and radio capacity.
Specifications for the Evolved Packet System (EPS) have been completed within the 3GPP and this work continues in the coming 3GPP releases. The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the LTE radio access, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a variant of a 3GPP radio access technology wherein the radio base stations are directly connected to the EPC core network rather than to RNCs. In general, in E-UTRAN/LTE the functions of a RNC are distributed between the radio base stations, e.g., eNodeBs in LTE, and the core network. As such, the RAN of an EPS has an essentially “flat” architecture comprising radio base stations without reporting to RNCs.
In today's mobile user equipments (UE), multiple radio transceivers are packaged inside the same device. A UE can be equipped with external wireless system i.e. non-cellular communication systems. Examples of such external wireless systems which can be located on a cellular device or UE are LTE, WiFi, Bluetooth transceivers, Global Navigation Satellite System (GNSS) receiver, sports or medical related short range wireless devices, cordless telephone etc. Examples of GNSS are Global Positioning System (GPS), Galileo, Common Positioning. Architecture for Several Sensors (COMPASS), Galileo and Additional Navigation Satellite Systems (GANSS) etc.
There are a variety of user equipments and user equipments are referred with different technical and brand names e.g. USB-dongle, target device, mobile terminal, wireless terminal, wireless terminal used for machine type communication, wireless device used for device to device communication etc. FIG. 1 shows the 3GPP frequency bands around 2.4 GHz industrial, scientific and medical (ISM) bands. The transmit power of one transmitter may be much higher than the received power level of another receiver, which due to extreme proximity of these radio transceivers, can cause interference on the victim radio receiver.
Wi-Fi uses frequency band 2400-2495 MHz in the ISM band. This band is divided into 14 channels, where each channel has a bandwidth of 22 MHz, and 5 MHz separation from other channel with an exception of channel number 14 where separation is 12 MHz. The transmitter of LTE band 40 will affect receiver of WiFi and vice-versa. Since band 7 is a Frequency Division Duplexing (FDD) band so there is no impact on LTE receiver from Wi-Fi transmitter but Wi-Fi receiver will be affected by LTE Uplink (UL) transmitter. Bluetooth operates between 2402-2480 MHz, in 79 channels of 1 MHz bandwidth each. Therefore similar to Wi-Fi, there are interference between band 40 and Bluetooth as well as interference from band 7 UL to Bluetooth Receiver (RX).
Furthermore, the reception of GNSS in the ISM band, e.g. Indian Regional Navigation Satellite System that operates 2483.5-2500 MHz, can be affected by band 7 UL transmission.
In summary some examples of interference scenarios are:                LTE Band 40 radio transmitter (TX) causing interference to ISM radio RX        ISM radio TX causing interference to LTE Band 40 radio RX        LTE Band 7 radio TX causing interference to ISM radio RX        LTE Band 7/13/14 radio TX causing interference to GNSS radio RX        
Note that the frequency bands and radio technologies discussed above are just examples of different possible scenarios. In general the interference can be caused by any radio technology and in any neighboring or sub harmonic frequency band.
To avoid interference from LTE transceiver to other technologies, some interference avoidance solutions can be used in the UE or by the network. Interference avoidance solution can either be done autonomously by the UE, or performed by the network based on an indication from the UE.
In the following the two methods are briefly described:
When a UE experiences a level of In Device Coexistence (IDC) interference that cannot be solved by the UE itself, the UE sends an IDC indication via dedicated Radio Resource Control (RRC) signaling to report the problems, so called Network-controlled UE-assisted Interference avoidance. Indications can be sent by the UE whenever it has problem in ISM DL reception, or in LTE DL reception. Part of the IDC indication message is interference direction, which indicates the direction of IDC interference. The triggering of IDC indication is up to UE implementation, i.e. it may rely on existing LTE measurements and/or UE internal coordination.
The information element, InDeviceCoexlndication, defined in LTE RRC specification, TS 36.331, Rel-11, v. 11.1.0 section 5.6.9 and also shown below describes the message sent by the UE to the radio base station when it experiences problem related to IDC.
The InDeviceCoexlndication message is used to inform E-UTRAN about the IDC problems experienced by the UE, any changes in the IDC problems previously informed, and to provide the E-UTRAN with information in order to resolve them.
Signalling radio bearer: SRB1
RLC-SAP: AM
Logical channel: DCCH
Direction: UE to E-UTRAN